1. Field of the Invention
The present invention relates to a multi-cylinder V-type internal combustion engine. More particularly, the present invention relates to a multi-cylinder V-type internal combustion engine provided with charge injectors which directly inject a fuel-air mixture into combustion chambers of the cylinders, in which routing passages are provided to route compressed air to the charge injectors.
2. Description of the Background Art
It is well known to provide an internal combustion engine, used as a power source for a vehicle such as a motorcycle, with charge injectors which directly inject fuel-air mixture into combustion chambers in cylinders. Such an internal combustion engine is disclosed, for example, in Japanese Patent Laid-Open No. 2004-301113.
In such internal combustion engines, the opening and closing of the charge injectors are controlled in accordance with the cycle of combustion operation of the internal combustion engine, and the charge injectors mix fuel and compressed air supplied from an air compressor, and inject the mixture into the combustion chambers to allow the internal combustion engine to operate. The charge injectors make it possible to achieve improved fuel efficiency during operation of the internal combustion engine.
In addition, a V-type internal combustion engine is a well known type of internal combustion engine in which a plurality of cylinders are provided on a crankcase such that the plurality of cylinders spaced apart from each other in a V-shaped configuration. The V-type internal combustion engine is advantageous since it is possible to make the internal combustion engine more compact, and to reduce vibration accompanying the operation of the internal combustion engine, for example. In particular, for vehicles such as motorcycles in which the mounting space for the internal combustion engine is limited, use of the V-type internal combustion engine is considered to be an appropriate choice.
The charge injectors are provided in a cylinder head portion of the internal combustion engine. Placement of the charge injectors in this location creates the problem of determining how to provide compressed-air supply channels which extend from the air compressor, annexed to the internal combustion engine, to the charge injectors.
Specifically, there has been a problem with regard to V-type internal combustion engines, since compressed air has to be supplied from the air compressor to respective head portions of the cylinders which are spaced apart from each other due to the V-shape. As a result, the assembly structure of the internal combustion engine becomes complicated due to the design of the compressed-air supply channels unless the disposition, branching or the like of the compressed-air supply channels is contrived.
In particular, with regard to the V-type internal combustion engines, there has been a problem that the compressed-air pressures become uneven between respective head portions of the cylinders, and the fuel mixing ratios in the charge injectors therefore become uneven unless the lengths of the compressed-air supply channels extending from the air compressor to the head portions (the charge injectors) of the respective cylinders are made even.
In addition, when the compressed-air supply channels are excessively cooled as the vehicle travels, the moisture contained in the compressed air condenses to form dew in the compressed-air supply channel. This is problematic since this dew can cause a malfunction of the charge injectors and operational failure of the internal combustion engine.
Meanwhile, although the compressed-air supply channels should not to be excessively cooled, the air compressor annexed to the internal combustion engine is required to be easily cooled as the vehicle travels in order to increase the air compression efficiency. Accordingly, the realization of a V-type internal combustion engine which satisfies the above conflicting demands and can solve the above problems is desirable.
The present invention has been made in consideration of the above current circumstances, and an object thereof is to provide a V-type internal combustion engine having a structure that can be easily assembled even if the compressed-air supply channels extend from the air compressor, which is annexed to the internal combustion engine, to the charge injectors in a contrived manner.
Another object of the present invention is to provide, in the same way, a V-type internal combustion engine in which respective lengths of the compressed-air supply channels extending from the air compressor to the charge injectors are made even.
Still another object of the present invention is to provide, in the same way, a V-type internal combustion engine of which the compressed-air supply channels are not excessively cooled even when the internal combustion engine is cooled as the vehicle travels, and which thus makes it possible to prevent condensation in the compressed-air supply channels from occurring.
Yet another object of the present invention is to provide, in the same way, a V-type internal combustion engine, including the air compressor annexed thereto, that is cooled as the vehicle travels, and which thus makes it possible to increase the air compression efficiency of the air compressor.